Vehicle steering has traditionally comprised of adjusting the vehicle wheels' toe angle, caster or camber or all three to direct travel of the vehicle. Camber caster, and toe are typically adjusted during maintenance of a vehicle. Toe angle is typically also constantly changed during driving by turning of the steering wheel, which motion is typically translated through the steering column to a steering gear box or steering rack that changes the angular position of the wheels.
Toe angle can affect steer angle as the suspension system is compressed or extended from straight position. These changes in toe angle can enhance steering or it can detract from vehicle performance depending on whether the wheel's toe angle follows the desired direction of travel or not. In straight ahead driving it is typically desirable for all four wheels to have a slightly toe-in orientation. In braking it is preferably that the front suspension be in compression and the rear suspension be in extension; this tends to result in a toe-out angle for all wheels. To correct this toe-out orientation, an active adjustment needs to be made to all wheels. For improved traction and steering stability while braking in a turn, it is desirable to have some wheels toe-in while other wheels toe-out.
In some cases, it may be desirable to adjust wheel toe angle of all four wheels to match one another, to improve turning fidelity and also to reduce drag and improve fuel consumption. In other cases, it may be preferably to adjust the toe angle of the rear or front wheels to oppose one another, for example to enhance braking speed and effectiveness. Adjustment and control of both of these aspects of the wheels' orientation are important to stable driving in a straight direction, as well as accurate turning.
U.S. Pat. No. 5,143,400 teaches an apparatus for active toe adjustment in which a complex system of measuring devices are used to sense vehicle motion or toe angle relative to each wheel. This data is then conveyed via a computer to a separate system comprising mechanical screw actuators and optical encoders, to then make secondary toe angle corrections.
U.S. Pat. No. 7,873,440 teaches an apparatus for controlling toe angle of a pair of wheels such that the wheel toe angles match one another. The apparatus includes an actuator and a separate sensor on each of only two wheels on a vehicle. The system is not designed for independent movement of all wheels of a vehicle to individual toe angles.
A need therefore exists in the art for a convenient and accurate system of vehicle toe angle and camber adjustment.